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plunger
04-19-2016, 12:59 PM
In Durban S Africa we are experiencing a severe drought. I have been asked to install a 120 meter borehole to a clients house. It is first pumped into a 2500l holding tank and from there goes through a fancy variable speed drive booster pump.

The water has been sent for tests but this is Africa so we must expect delays.The guys borehole 100meters down the road has e coli in the water so I expect the same. How could I kill the bacteria without him having to get a new mortgage on his house.?

Would it not be as simple as having a container and using the velocity of water in the bigger pipe creating a venturi system of sorts and dosing the main feed pipe by simply opening a tap. I see this used on urinals and kitchen sinks where it sucks disinfectant out of a 25 liter drum?

Toolguy
04-19-2016, 01:01 PM
Does UV light kill ecoli?

Fasttrack
04-19-2016, 01:10 PM
Interesting challenges you face... around here e. coli contamination is not too unusual but the remediation typically involves disinfecting the well, tank, pump, etc. by shocking the borehole with chlorine and then purging the system (e.g. leaving a tap on) until the chlorine has been flushed. The water is then typically safe to drink unless there is a serious, continuing contamination problem due to the proximity of a septic system, etc. So my first question would be: are you close to sources of contamination? Has the borehole been cased? Usually you install casing to prevent surface water (contaminated with lots of nasties) from polluting the borehole, which should fill with groundwater that has been filtered through lots of bedrock before collecting in the hole. If casing has been used and the geology of S. Africa (in regard to groundwater and natural filtration) is similar to North America, then I would expect a single disinfection via chlorine shock would be enough to kill any bacteria that contaminated things during the drilling and installation of equipment.

If this water is for drinking and it is "permanently" contaminated, then the only option I'm familiar with is a fairly involved (but not necessarily expensive) setup to address all possible water quality issues. If the water is soft and relatively pure except for bacteria, they make UV disinfectors that kill the bacteria without adding nasty chemicals. A reverse-osmosis filter with active carbon will remove many pathogens and the toxins they produce, so that's another option. You could find a small one that's just big enough to provide drinking/cooking water and the rest of the water could be left untreated.

I'm interested to hear how this turns out - I'm no expert but had to deal with some water quality issues at the house I recently bought.

Fasttrack
04-19-2016, 01:11 PM
Does UV light kill ecoli?

Yes: https://www.uswatersystems.com/us-water-whole-house-professional-grade-ultraviolet-system-10-gpm.html?fee=10&fep=12770&gclid=CKSVtfeYm8wCFYsAaQodD_cNlQ

Illinoyance
04-19-2016, 01:35 PM
I have been away from the water well business for many years. Here is what I remember. There was a feeder that mounted to the well head that dropped chlorine pellets directly into the well casing. It was controlled by a timer and only operated when the pump was running. An alternative is use of a chemical feed pump to feed chlorine solution into the holding tank. It would run only when the well pump was running. The chlorine pellets I referred to were probably sodium or potassium hypochlorite. Chlorine solution could be either household bleach or commercial bleach which is stronger, again hypochlorite.

Black Forest
04-19-2016, 01:47 PM
We use a UV light treatment to our water. It kills the nasties in the water. I prefer that to chemical treatment.

plunger
04-19-2016, 01:48 PM
From what I have been told the first section was clay and sand so they put in some steel pipes. It then got into some fairly stable substrate, I think dolomite was the term used?This whole area has no waterborne sewerage and all the houses are on septic tanks. Its about 30 meters from the Indian Ocean,I am suprized its not pumping salt.The water is standing at ten meters below the surface.The borehole is going to pump the water into a small holding tank of 2500l before it is pumped to the house.

RancherBill
04-19-2016, 04:07 PM
This is what we did for our well. It worked for us.

http://www.waterandhealth.org/newsletter/private_wells.html

Carm
04-19-2016, 04:11 PM
Plunger
Couple ways to do this.
Dose the holding tank w/sodium hypochlorite(SH). I recall lots of people have swimming pools there, a pool supply would have the chemical.
A low dose in the tank prevents increased contamination. Best if the tank is kept cool and dark.

Install a feeder using SH, works as you thought in your OP. Hayward is a vendor stateside, no doubt others with the same principle. The dose can be adjusted to flow rate/desired PPM. Again, a pool item.

Install a UV line for potable water. The system has fine print which you need to study up on (meaning there are hazards and requirements of wattage/flow rate and clarity of throughput) and will require maintenance, though all will.

Shocking the bore w/SH is problematic plus it's hard on the casing, if steel. Better to treat above ground.

When there was a drought in the highveldt there were strict limits on allowed usage. If that is not the case for this job, contaminated water can be used for the garden, washing cars, laundry. So a small treatment system may suffice for personal hygiene and drinking water.

P.S. Do you still have Castle lager?
P.P.S. Dolomite is a form of limestone

plunger
04-19-2016, 04:31 PM
Plunger
Couple ways to do this.
Dose the holding tank w/sodium hypochlorite(SH). I recall lots of people have swimming pools there, a pool supply would have the chemical.
A low dose in the tank prevents increased contamination. Best if the tank is kept cool and dark.

Install a feeder using SH, works as you thought in your OP. Hayward is a vendor stateside, no doubt others with the same principle. The dose can be adjusted to flow rate/desired PPM. Again, a pool item.

Install a UV line for potable water. The system has fine print which you need to study up on (meaning there are hazards and requirements of wattage/flow rate and clarity of throughput) and will require maintenance, though all will.

Shocking the bore w/SH is problematic plus it's hard on the casing, if steel. Better to treat above ground.

When there was a drought in the highveldt there were strict limits on allowed usage. If that is not the case for this job, contaminated water can be used for the garden, washing cars, laundry. So a small treatment system may suffice for personal hygiene and drinking water.

P.S. Do you still have Castle lager?
P.P.S. Dolomite is a form of limestone
Hose pipes are banned but its so bad the water is simply switched off.the rock was black so I guess its not limestone more like slate .there are not that many pools as the sea is right on your doorstep. its a beautiful little town but is prime estate so its hard to afford living there, I cant.
Lion lager is no more but castle lager is still going strong at S A breweries.I think south african breweries is one of the biggest in the world?

camdigger
04-22-2016, 10:22 AM
Bacteria of one sort or another are more common in well water than is commonly believed.

As has been previously posted there are dosing systems that drop chlorine/bleach tablets down the well bore. There are also dosing systems that will dose a holding tank.

The system for wells has been described above. The system for holding tanks is similar, but is connected in parallel with either the feed pump or the delivery pump (pump in vs pump out). The system I have has the well pumping into a 800 l holding tank. The incoming water is controlled by a float valve (commonly available for stock waterers.). The water flows from the float valve through a stainless strainer the chlorine tablets are dropped into. The water is pumped out of the holding tank by a second submersible pump in the holding tank, but goes through a charcoal filter to remove the chlorine and dead bugs. The filter is identical to a water softener cylinder with different media. The filter has a backwash head commonly available from water treatment firms like Culligan. In operation, the backwash is set to happen every 24 to 48 hours in the wee hours when water consumption is unlikely. The biggest issue we have is there are just enough interruptions in our power service that the clock on the backwash head goes out of synch and the system back washes at the wrong time. The submersible in the holding tank is controlled by a second pressure switch on a tank between the holding tank and filter.

FYI, I seem to recall 200 ppm as the minimum amount of chlorine to reliably kill the bugs. 400 ppm is the maximum recommended amount of chlorine in the holding tank. There are test kits for chlorine available from pool supply companies that use either test strips or a test vial and an indicator liquid. These kits have a Color scale to determine Cl content.

The system I have is commercially available here in North America, but a skilled plumber should be able to assemble one from local parts..... I could be persuaded to send a couple pictures if an email was pm d. I doubt the patent is still valid, the design is over 25 years old.